1. Field of the Invention
The present invention relates generally to the fabrication of magnetic heads for disk drives and particularly to the manufacture of magnetic read heads.
2. Description of the Prior Art
In recent years there has been a constant effort to increase the performance of hard disk drives by increasing the a real data storage density of the magnetic hard disk. This is done by reducing the written data track width, such that more tracks per inch can be written on the disk. Read sensors, of which one type is referred to as a Giant Magneto-Resistive (GMR) head, have been developed to read trackwidths smaller than 130 nm. The manufacture of these read sensors depends upon the ability to ion mill the sensor to these very small dimensions, and to reliably lift-off the deposited layer materials.
There are two configurations of read heads in common use in the industry today. These are called Current Perpendicular to the Plane (CPP), and Current In the Plane (CIP). In the CIP configuration, current flows from side to side; that is from a lead through the read sensor to another lead. A cross section view of a CIP slider is shown in FIG. 4, which generally includes a write head portion 26 and a read head portion 28. For CIP read heads, the read sensor 40 is generally sandwiched between two insulation layers, usually designated gap 1 34 and gap 2 36 which are made of non-conductive material, to keep the circuit from shorting out. These are further sandwiched by magnetic shield layers S1 30 and S2 20. For the purposes of this discussion, the read head 28 will be considered to be in CIP configuration.
A typical CIP read sensor 40, and lead layer stacks 55, including lead layers 56, hard bias layers 58 and seed layers 60, are shown in FIG. 5. The sensor 40 is generally made up of a number of layers, to make a sensor stack 42, which generally includes an Anti-ferromagnetic (AFM) layer 44, a pinned magnetic layer 46, a spacer layer 48, a free magnetic layer 50 and a cap layer 52. The sensor stack 42 is built on the gap 1 insulating layer 34, as discussed above.
The lead layer stacks 55 are typically made up of lead layers 56 built on hard bias layers 58, built in turn on a seed layer 60. The hard bias layers 58 are generally aligned with the free layer 50 of the sensor stack 42, and act to give a bias direction to the magnetic domains in the free layer 50.
This configuration of sensor is referred to as a Giant Magneto-Resistive (GMR) read sensor, and typically the sensor stack 42 is formed first, and the lead layer stacks 54 are formed around them. The general methodology used in the prior art for forming the read head and leads is shown in FIGS. 6-8 (Prior art).
FIG. 6 (prior art) shows that the sensor stack 42 including AFM layer 44, pinned layer 46, spacer layer 48, free layer 50 and cap layer 52 is built on gap1 34. A photomask 62 is then formed on the sensor stack 42 and an ion milling beam 64 is then used to shape the sensor stack 42 to that shown in FIG. 7 (prior art).
The lead layer stacks 55, which generally include seed layers 60, hard bias layers 58, and lead layers 56, are then formed around the sensor stack 42, before the photomask 62 is removed to complete this stage of the process.
This manufacturing process involves ion milling of the sensor stack 42. This milling step also partially mills the underlying gap1 layer 34. A potential disadvantage to the prior art process is the effect of ion milling on the GMR sensor 40 and gap1 34, and the growing demands on the associated lithography and liftoff process. Bombardment of energetic ions on a GMR sensor during milling may create damage such that its magnetic performance is undermined. This damage starts at the edges of a read track and propagates inwards. Thus the consequences will likely become more severe as the physical width of the read-head is reduced.
It is also known that uncontrolled milling of a gap layer can create catastrophic Electrostatic Discharge (ESD) problems. Again this may be attributable to physical damage to the gap material by ion bombardment.
Finally, the prior art process is preceded by increasingly complex photolithography and liftoff operations in order to accommodate shrinking dimensions. The milling process requires a masking material that has sufficient selectivity in order to retain adequate thickness for subsequent liftoff. With shrinking size, the required stack thickness may not be sustainable. Thus alternative methods may be required.
Thus there is a need for a method of fabrication for read sensors which does not involve subjecting the sensor stack materials to damage from ion milling, does not subject the gap1 layer to ESD damage and does not involve complicated photolithography and liftoff operations.